The compressor and turbine section of a turbine engine can include rotors with discs on which a plurality of blades are attached. The blades are arranged into one or more rows spaced axially along the rotor. The blades in each row are disposed about the periphery of the disc.
FIG. 1 shows a common system for attaching the blades 10 to a disc 12. The disc 12, which is shown in partial section, provides a slot or groove 14 extending about the periphery of the disc 12. The slot or groove 14 can have any of a number of configurations.
Each blade 10 has a root portion 17 at its base which is closely profiled to match the shape of the disc groove 14. Each blade 10 is retained by sliding the root 16 of the blade 10 into the disc groove 14. As a result of the close match in size and shape of the blade root 16 and rotor groove 14, motion of the blade 10 in the axial and radial direction is closely restrained. The slot 14 in the disc 12 permits a fan of blades 10 to be arranged about the periphery of the disc 12. The blades 10 are spaced apart peripherally and the resulting voids in the slot 14 between the roots 16 of adjacent blades 10 are filled with spacers 18.
The disc slot 14 typically provides a profile having lateral recesses 15 for receiving corresponding projections 17 of the attachment lugs 16 of the blades 10 and spacers 18. It is these substantially mating recesses 15 and projections 17 that secure the blades 10 and spacers 18 axially and radially. Because of the projections 17, the attachment lugs 16 of the blades 10 and spacers 18 cannot be directly inserted into the slot 14 in their operational orientation. Instead, the root portion 16 of these components must first be inserted sideways, with the projections 17 extending along the slot 14 and then rotated to the final orientation with the projections 17 extending into the lateral recesses 15.
As blades 10 and spacers 18 are installed in the slot 14, the remaining space in the slot 14 permits the next blade 10 or spacer 18 to be installed as discussed above. However, when the blade 10 and spacer 18 array is near complete installation, there is not sufficient space remaining in the slot 14 to permit insertion and rotation of the final spacer 18. To address this space constraint, multipart spacers have been developed that can be installed in pieces without the need to rotate into final position. Typically, two end supports are positioned into mating engagements with the recessed sides of the slot and a filler piece is interposed between the end supports. However, under the great centrifugal forces encountered during operation of the turbine, these multipart spacers can come apart and dislodge, causing extensive damage to the turbine engine.